Ball-Striking Device and Method for Producing Same

ABSTRACT

The present invention relates to a ball-striking device ( 1 ), in particular a tennis, squash, or badminton racket, having a head frame ( 2 ), which comprises a striking surface, is of a hollow design, and is produced from plastic, in particular from a fiber-reinforced plastic, and a shaft formed thereon with grip, wherein the striking surface ( 12 ) is defined by at least one string ( 8 ), which is tensioned in a crisscross manner and which forms string portions fastened substantially in parallel to one another on the head frame, wherein the anchoring of the string portions on the head frame ( 2 ) is performed via retainers ( 20 ) which are fastened on the inner side of the head frame so that they each extend substantially perpendicularly in relation to the striking surface, whereby the ends ( 10 ) of the string portions clamped in the retainers ( 20 ) can be laterally deflected upon impact of a ball. With the goal of specifying such a ball-striking device and a method for the production thereof, in which the anchoring of the string portions on the head frame is performed via retainers which may be arranged precisely and easily in the head frame and are also suitable for a mass production method, it is provided that the retainers ( 20 ) are open toward one of the two sides of the striking surface ( 12 ) and/or are freely accessible from one of the two sides of the striking surface ( 12 ) for clamping the string which defines the striking surface.

The present invention relates to a ball-striking device, in particular a tennis, squash, or badminton racket, having a head frame, which comprises a striking surface, is of a hollow design, and is produced from plastic, in particular a fiber-reinforced plastic, and a shaft formed thereon with grip, wherein the striking surface is defined by at least one string, which is tensioned in a crisscross manner and which forms string portions fastened substantially in parallel to one another on the head frame, wherein the anchoring of the string portions on the head frame is performed via retainers which are fastened on the inner side of the head frame so that they each extend substantially perpendicularly in relation to the striking surface, whereby the ends of the string portions clamped in the retainers can be laterally deflected upon impact of a ball. Furthermore, the invention relates to a method for producing such a ball-striking device.

Hereafter, the term “ball-striking device” or “racket” in short is to be understood for the purpose of the present invention in particular as tennis, squash, or badminton rackets; however, the significance of the term is not restricted in the present case to these rackets per se, but rather relates to any type of ball-striking devices, which have a striking surface and the striking surface of which is defined by at least one string which is tensioned in a crisscross manner.

A ball-striking device of the type mentioned at the outset is known, for example, from EP 2 164 579 B1. It has a head frame, which comprises a striking surface, is of a hollow design, and is produced from a fiber-reinforced plastic, and on which a shaft formed having a grip, wherein the striking surface is defined by at least one string, which is tensioned in a crisscross manner and which forms string portions fastened substantially in parallel to one another on the head frame. The anchoring of the string portions on the head frame is performed via multiple curved retainers, which are laminated into the inner side of the head frame such that they each extend substantially perpendicularly in relation to the striking surface, whereby the ends of the string portions clamped in the retainers can be laterally deflected upon impact of a ball. In this solution known from the prior art, two retainers are required in each case per clamped end of a string portion, to implement two string portions extending in parallel at a defined distance. However, it is difficult to laminate in the retainers correctly aligned in relation to one another. In addition, stringing such a racket takes a relatively long time, because the string has to be threaded through a plurality of retainers and has to be tensioned in portions. In particular, it has been shown that the stringing of the racket takes longer than the stringing of conventional rackets, in which the string is guided through boreholes on the head frame.

It is therefore the object of the present invention to specify a ball-striking device and a method for the production thereof, in which the anchoring of the string portions on the head frame is performed via retainers, which may be arranged precisely and easily in the head frame and are also suitable for a mass production method.

This object is achieved according to the invention by a ball-striking device having the features of Claim 1 and with regard to the method by the subject matter of Claim 12. It is accordingly provided that a ball-striking device is specified, in which the retainers are open toward one of the two sides of the striking surface and/or are freely accessible from one of the two sides of the striking surface for clamping the string which defines the striking surface.

The solution according to the invention has an entire array of substantial advantages over the ball-striking devices known from the prior art. Thus, due to the retainers which are open toward one of the two sides of the striking surface or the retainers being freely accessible for clamping the string which defines the striking surface, stringing of the ball-striking device can be produced rapidly and easily. In addition, a high-precision stringing pattern is achieved, which has outstanding playing properties.

Advantageous refinements are specified in the dependent claims.

It is accordingly provided that a set of retainers is provided for anchoring the string portions on the head frame, which comprises a first number of retainers having a first predetermined length in the circumferential direction of the head frame, at least one second number of retainers having a second predetermined length in the circumferential direction of the head frame, and optionally at least a third, fourth, and fifth number of retainers having a third, fourth, and fifth predetermined length in the circumferential direction of the head frame. Ball-striking devices typically have an ellipsoidal shape, on each of the two large half-axes of which, proceeding from the center point, the first number of retainers having the smallest predetermined length is located. These define the size of the stringing pattern, which generally consists of largely equilateral rectangles. As a result of the ellipsoidal shape of the head frame, retainers having different lengths in the circumferential direction of the head frame enable a substantially equal and exact stringing pattern. At the same time, an arrangement of multiple retainers, as is known from EP 2 164 579 B1, is simplified in that a single retainer according to the invention is sufficient to define two string portions extending in parallel.

The string is the only material which comes directly into contact with the ball. The stringing of the string therefore decides on playing properties such as control, spin, power, feeling, and comfort of the ball-striking device. A high stringing weight guarantees more control, but requires more force; with softer stringing, a greater force and final velocity (power) of the ball can be generated with less exertion. A soft stringing is between approximately 18-21 kg, a normal stringing is between approximately 22 and 25 kg, and a hard stringing is between approximately 26 and 28 kg. While there is a variety of stringing patterns (for example, 14×16, 14×18, 16×15, 16×16, 16×17, 16×18, 16×19, 16×20, 18×18, 18×19, 18×20, and 18×21, wherein the first number defines the number of the longitudinal strings and the second number defines the number of the transverse strings), the stringing patterns 16×19 and 18×20 differ in that 16×19 typically offers more power and spin, while 18×20 enables more control with longer durability of the strings.

Head frame sizes are frequently in the classes midsize (<97 in.²/625 cm²), mid-plus (98-105 in.²/630-675 cm²), oversized (106-115 in.²/680-740 cm²), and super oversized (>116 in.²/750 cm²). The head frame size can vary in accordance with the number of the strings and the type of the stringing. In the meaning of the invention, the number and width of the retainers used are dependent on the head frame geometry and are especially adapted thereto.

The retainers used according to the invention preferably each comprise, in the state fastened on the head frame, a retainer portion protruding therefrom and a fastening portion anchored inside the head frame. The protruding retainer portion is used for easy and precise hooking of the string during the stringing. The fastening portion which is located inside the frame offers the advantage of secure anchoring of the retainer in the head frame.

To further improve the anchoring of the fastening portion and therefore the loadbearing capacity, the fastening portion of each retainer has longitudinal and transverse structures for the formfitted and friction-locked anchoring inside the head frame. “Longitudinal and transverse structures” means that the fastening portion has, for example, a longitudinal portion extending into the head frame, on which transverse webs or projections are formed. Independently of the formation of the retainer portion, for example, either open toward one side or freely accessible from one side, in particular hooked, preferably oval-hooked, or closed toward both sides, in particular ring-shaped, the fastening portion of each retainer is preferably embedded between two frame halves which define the head frame. This offers the advantage that by using prefabricated semifinished products, a head frame is producible rapidly and easily using routine means. A durable anchoring of the retainer in the head frame results by way of the corresponding embedding, which also readily withstands high repeated stresses.

It is preferably provided that the head frame is formed by two tubular prepregs which define the frame halves, and which define a double-walled circumferential transverse web extending approximately in parallel to the striking surface approximately at the height of the striking surface, wherein the fastening portions of the retainers are each embedded between the wall portions of the two tubular prepregs defining the double-walled transverse webs and are therefore fixedly anchored. A friction-locked and formfitted anchoring of the retainers in the head frame is thus obtained in a simple manner. When the prepregs are inflated, they press in a formfitted manner against the fastening portions of the retainers. This form fit is fixed by the curing, so that a long-lived and robust anchoring of the retainers in the head frame results.

It has proven to be advantageous for playing if the internal radius of the retainers is in a range from 0.5 to 1.9 mm, in particular 0.5 to 1.0 mm. This radius is adapted to the diameter of typically used strings, so that the ends of the string portions clamped on the retainers can be laterally deflected upon impact of a ball and excessively strong wear as a result of friction of the string during the deflection procedure is avoided. In addition, it is also conceivable that the surface of the retainers is treated using a surface finishing method on the side facing toward the string, which reduces the coefficient of friction with the surface of the retainer interacting with the string.

It is preferably provided that the first predetermined length (L1) of the first number of retainers is in a range from 9-11 mm and/or the first number of retainers of the first predetermined length (L1) is 12 to 20, in particular 16, and/or the second predetermined length (L2) of the second number of retainers is in a range from 10-11 mm and/or the second number of retainers of the second predetermined length (L2) is 6 to 14, in particular 10, and/or the third predetermined length (L3) of the third number of retainers is in a range from 11-13 mm and/or the third number of retainers of the third predetermined length (L3) is 2 to 10, in particular 6, and/or the fourth predetermined length (L4) of the fourth number of retainers is in a range from 16-18 mm and/or the fourth number of retainers of the fourth predetermined length (L4) is 2 to 8, in particular 4, and/or the fifth predetermined length (L5) of the fifth number of retainers is in a range from 20-22 mm and/or the fourth number of retainers of the fourth predetermined length (L5) is 1 to 4, in particular 2. The best possible adaptation of the stringing pattern to the shaping of the head frame, which can generally be embodied as ellipsoidal to a more or less pronounced extent, for achieving a desired stringing pattern is achieved by retainers formed in this way. Furthermore, an exact, rectangular stringing pattern within the main striking region (sweet spot) is thus created. The main striking region is the region of the stringing pattern in which the stringing is defined by substantially identical or equivalently dimensioned string squares. Outside this region, the string portions which are tensioned in a crisscross manner each delimit rectangular panels of greater or lesser length.

During the production of a racket according to the invention, it can be advantageous, in particular for higher piece counts, to produce them in an automatic or partially automatic method. For this purpose, the retainers of predetermined length are each identified with a character, which is provided for the purpose of typing, in particular characters which are visually and/or haptically recognizable or are also readable in any other readable or automatically analyzable form, which reflects the type of a predetermined length (L1; L2; L3; L4; L5). However, this can also be advantageous in the case of manual processing and in particular when equipping a holding device for the retainers, because rapid and accurate equipping of the holding device with retainers provided at the respective position is enabled. For facilitated positioning of the retainers, they are preferably initially inserted into an insertion device, and then positioned together with the insertion device in relation to the holding device for the retainers, before subsequently the retainers are each fixed in the region of their retainer portions inside the holding device. The insertion device prevents the retainers from changing their predetermined position during the fixing thereof in the holding device, for example, slipping.

According to the invention, a lateral gap (S) is defined between retainer and head frame, wherein the width of this gap is in the range from 1.0 to 2.0 mm, in particular in a range from 1.5 to 1.7 mm. This gap enables lateral clamping of the string and is dimensioned so that the string can be hooked without problems on the retainer portion of the retainer for the stringing.

Furthermore, it is possible that the ends of the retainers, over each of which the string defining the striking surface is deflected, are rounded, whereby wearing or damage to the string in playing operation is precluded and the playing properties of the racket are further improved.

Furthermore, it is also provided according to the invention that a method for producing a ball-striking device is specified, in which the retainers are positioned in relation to a mold, within which a head frame of a ball-striking device is produced, such that the fastening portions of the retainers protrude into the head frame during the production thereof and are enclosed by the material thereof. Such a method offers the advantage of rapid and simple production ability of a head frame having retainers anchored therein. In this case, the head frame can be produced by injection molding, but in particular also using a fiber-reinforced plastic.

It is particularly preferable if the method according to the invention has the following method steps:

-   -   positioning a first prepreg tube in a first, for example, lower         head frame mold;     -   positioning a second prepreg tube in a second, for example,         upper head frame mold;     -   positioning a holding device for the retainers, which are held         in the correct positions therein, between upper and lower head         frame mold such that the retainers, which define the fastening         portions, protrude with a gap between the first and second         prepreg tube;     -   forming and curing the prepreg tubes in the closed head frame         mold while embedding the retainer fastening portions; and     -   demolding and cooling the finished head frame having retainers         fixedly anchored on the frame inner side.

A ball-striking device having retainers which are arranged with high precision, and in particular are uniformly aligned, for producing a string stringing having outstanding playing properties may thus be produced rapidly and easily. The retainers are under high force action during the inflation of the prepreg tubes and during the demolding procedure. The holding device ensures that the retainers maintain their provided positions in relation to the head frame to be produced. Discards in the production process are thus substantially avoided. The predefined position and alignment of the retainers are always ensured in comparison to the prior art. Equipping an insertion device with retainers is also particularly advantageous in this context, by means of which reliable and accurate positioning of the retainers within the above-mentioned holding device is possible, without the risk existing that the retainers will change their position during fixing of the retainers in the holding device.

To produce a ball-striking device having head frame and retainers arranged therein, shaft with grip and a throat arranged in between, it is furthermore provided that a method is specified for producing a ball-striking device, in which the frame, which consists of head frame having retainers and also shaft having grip and throat, is produced in one method step.

Further details and advantages of the invention will be explained in greater detail on the basis of an exemplary embodiment illustrated in the drawing.

In the figures:

FIG. 1: shows the head frame of a ball-striking device according to the invention within a production mold in cross section and enlarged scale;

FIG. 2: shows a top view of an exemplary embodiment of a ball-striking device designed according to the invention, specifically a tennis racket;

FIG. 3: shows a detail view of a retainer embedded in the head frame in a top view;

FIG. 4: shows a perspective in a top view and a side view in each case of two retainers of different predetermined length L;

FIG. 5 shows an enlarged view (perspective, top view, side view) of an exemplary retainer according to FIG. 4;

FIG. 6: shows a perspective of a lower part of a holding device for retainers;

FIG. 7: shows a perspective of a fully assembled holding device for retainers;

FIG. 8: shows a perspective of a lower mold half for the production of a ball-striking device according to the invention with positioned holding device for retainers;

FIG. 9: shows a perspective of a ball-striking device lying in a lower mold half with holding device after removal of an upper mold half;

FIG. 10: shows an alternative embodiment of a head frame having semi-oval retainers embedded inside a transverse web, in cross section; and

FIG. 11: shows insertion devices for the positioning of the retainers in a perspective view.

The elements essential for the immediate understanding of the invention will now be shown.

FIG. 1 shows a cross section A-A through the head frame 2 of a ball-striking device 1 according to the invention inside a production mold. In this case, a retainer 20 is embedded between two halves 4, 6 of a head frame 2. The head frame 2 is formed by two frame halves 4, 6, which are each made of two tubular prepregs 4, 6. Approximately at the height of the striking surface 12, the section shows a double-walled circumferential transverse web 40, which extends approximately in parallel to the striking surface 12. The retainers 20 are held for positioning between an upper holding tool 34 and a lower holding tool 32. The upper and the lower holding tools 32, 34 form a holding device 30. The holding device 30 is used for holding the retainer(s) 20 in the correct position between an upper 52 and a lower 50 head frame mold such that the retainers 20 are enclosed with the fastening portions 22 thereof in a region between the two prepreg tubes 4, 6. The two prepreg tubes 4, 6 are then formed and cured with the supply of pressure and heat between an upper mold 52 and a lower mold 50. The fastening portions 22 of the retainers 20 are each embedded between the wall portions 42 of the two tubular prepregs 4, 6, which define the double-walled transverse webs 40, and fixedly anchored. Of course, the two wall portions 42 of the two prepregs 4, 6 fuse together during the production of the head frame to form a unified material transverse web 40, wherein in this case the fastening portions 22 of the retainers are fixedly embedded and anchored in this transverse web 40, which then has unified material.

As already mentioned above, each retainer 20 has a fastening portion 22 embedded in the head frame 2. The fastening portion 22 essentially consists of a longitudinal structure 26 and a transverse structure 27. At the intersection of the longitudinal and transverse structures 26, 27 of each fastening portion 22, a character 14 applied for the purposes of typing—the number “2” in FIG. 1—is provided. The character 14 applied for the purpose of typing corresponds to the type and/or the length (L1 to L5) of the retainer 20 in the circumferential direction of the head frame. The applied character is essentially used for the identification and later placement in the holding device 30. For this purpose, a plurality of retainers 20 is fixed in the holding device 30 and subsequently positioned on the first prepreg tube 4 in the first, lower head frame mold 50. Subsequently, the mold 50, 52 is closed and the retainers 20 are thus positioned between the first and a second prepreg tube 4, 6, from which the head frame 2 is produced. Subsequently, forming and curing of the prepreg tubes 4, 6 is performed in the closed head frame mold with the supply of pressure and heat, whereby the fastening portions 22 of the retainers 20 are embedded in a friction-locked and formfitted manner between the two head frame halves formed from the prepreg tubes 4, 6. After cooling, the finished produced head frame 2 can be demolded having the retainers 20 fixedly anchored on the frame inner side.

FIG. 2 shows a top view of a ball-striking device 1 of an exemplary embodiment according to the invention. The racket 1 substantially consists of the head frame 2, the stringing arranged therein, which defines a striking surface 12 (formed from a plurality of intersecting string portions), and also a racket shaft 17, which comprises a grip 16 and a so-called throat 18, via which the shaft is connected to the head frame. The throat 18, which is produced from two webs or prepreg tubes 4, 6 (see FIG. 1), which originate from the shaft 17 and diverge in a fork shape, results in an integral racket 1 jointly with the shaft 17 and the head frame 2. The illustrated embodiment, which comprises a hollow profile closed to the outside, consists of a material suitable for the intended field of use of a piece of sports equipment, for example, of fiber-reinforced plastic. The striking surface 12 is formed by a string 8 (see FIG. 3), which is held on the head frame 2 under predetermined tension. The string is typically fastened and tensioned by means of a tensioning device on the frame. Inside the main striking region 13, the striking surface 12 has a checkerboard stringing pattern consisting of substantially identical squares. The goal of a racket produced according to the invention is a higher degree of accuracy in the positioning of the retainers 20 (see FIG. 1), so that the above-mentioned stringing pattern is obtainable. Outside the main striking region 13, the stringing pattern deviates from the checkerboard shape. The intersecting string portions then delimit rectangles of greater or lesser length.

FIG. 3 shows an enlargement of a retainer 20 embedded in the head frame 2. The fastening portion 22, which is located inside the head frame 2 and is fixedly anchored in the head frame 2, is indicated accordingly. A string 8 is wrapped around the two ends of the retainer portion 24, which protrudes out of the head frame, of the retainer 20. The retainer has in particular, but not exclusively, rounded corners 29 in the region of frontal ends. The rounded corners prevent rubbing of the string 8 and unintentional damage thereto by sharp edges, as is typical in conventional rackets having boreholes in the head frame. The string deflection surface 46 of the retainer portion 24 of the retainer 20 protruding out of the head frame, against which the deflected portion of a string presses, drops off slightly on both sides in the circumferential direction of the head frame from a plane of symmetry 47 of the retainer 20. This deflection surface is preferably curved toward the striking surface or away from the inner side of the head frame in the circumferential direction of the head frame, wherein the radius is in the range from 80-150 mm.

FIG. 4 shows a first type of retainer 20 and a fifth type of retainer 20, each of different predetermined length L1 and L5. To produce a uniform and substantially checkerboard string stringing of the ball-striking device 1, the different length L is used for the adaptation to various frame geometries, which are generally substantially ellipsoidal, and can be of different sizes. In general, a larger number of retainers of a shorter predetermined length and a smaller number of retainers of a longer predetermined length are required for this purpose.

FIG. 5 shows a perspective of a retainer 20, a frontal view having a frontally attached typing character “2”, and a top view of this retainer 20. The top view shows a line of symmetry 47 and the rounded corners 29 of the retainer portion 24 (see FIG. 3). A character 14 applied for the purpose of typing—number “2” here—is provided at an intersection of the longitudinal and transverse structures 26, 27 of the fastening portion 22 of the retainer 20. The character 14, which is applied for the purpose of typing, indicates the type or the length L1, etc., of a retainer 20. The applied character 14 is essentially used for identification and later processing in a positioning and holding device 30 (see FIG. 7). The longitudinal and transverse structures 26, 27 of the fastening portion 22 (see FIG. 3) are used for the friction-locked and formfitted anchoring of the retainer 20 in the head frame and are optimized and adapted with respect to the shaping thereof to the material of the plastic used, in particular a prepreg tube which is used, and the wall thickness thereof. It is substantially important that the plastic presses in a formfitted manner, without shrinkage cavities or gas bubbles, against the outer side of the retainer 20. For this purpose, the pressure during inflation of the prepreg tube together with the curing temperature used also has to be selected such that this is ensured. Furthermore, the above-mentioned parameters have to be selected accordingly so that force transmission, which is required for typical stresses of a ball-striking device, between head frame and the retainers 20 embedded therein can thus be absorbed in a friction-locked and formfitted manner.

FIGS. 6 and 7 show a lower holding tool 32 and an upper holding tool 34, which together form a holding device 30. The retainers 20 can be inserted, preferably in a precisely fitted manner, between the holding tools 32, 34. For this purpose, a defined number of retainers 20 is inserted into the lower holding tool 32, for example, and subsequently the upper holding tool 34 is laid over it in a precisely fitted manner. The lower holding tool 32 has multiple threaded boreholes 35, whereby the upper and lower holding tools can be screwed together with one another, and the retainers 20 are held against mechanical stress in a desired position. The holding tool can have multiple material recesses 38. After the production of a ball-striking device in a forming and curing method according to the teaching according to the invention, the screw connection 36 of the holding device 30 can be detached again. This offers the advantage that the holding device 30 is reusable and can be used in the scope of a mass production method.

FIG. 8 shows a lower mold 50 for producing a ball-striking device 1 having an inserted holding device 30 having retainers 20. At the lower end of the lower mold 50, compressed air inlets 54 are provided, via which the prepreg tubes 4, 6 (see FIG. 1) can be inflated during the production method according to the invention. FIG. 9 shows a perspective illustration of a ball-striking device 1, which is still to be demolded but is substantially finished, having head frame 2, throat 18, and shaft 17 including grip 16, and also retainers 20 fixedly anchored in the head frame 2.

It is to be noted here that instead of the above-mentioned “one-piece” construction, constructions having head frame, on the one hand, and separately formed-on shaft and/or grip and/or open or closed throat are also conceivable. The above-described measures according to the invention are applicable for all of these constructions.

FIG. 10 shows an alternative embodiment of a retainer 23, which is embedded inside a transverse web 40 of the head frame 2, in cross section. The retainer 23 is designed as semi-oval shaped in cross section, wherein the longer branch having the larger curve radius is used as the fastening portion and the shorter branch having smaller curve radius is used as the retainer portion which protrudes freely beyond the inner side of the head frame. This retainer portion is freely accessible from one side of the striking surface, i.e., the stringing of the ball-striking device, for example, tennis racket, takes place via this free access or via the gap between the free end of the retainer portion and the inner side of the head frame facing toward this free end. Otherwise, the production of the above alternative is performed similarly to the production of the embodiment according to FIGS. 1 to 8. FIG. 11 also shows an example of an insertion device 44, by means of which the retainers are held securely in position and introduced into the holding device 30, so that during the screwing together of the holding tools 32, 34, the retainers 20 cannot change the predetermined position thereof. The insertion device 44 facilitates the positioning of the retainers 20 in the holding device 30.

LIST OF REFERENCE NUMERALS

1 ball-striking device

2 head frame

4 first prepreg tube

6 second prepreg tube

8 tensioned string

10 ends of the string portions

12 striking surface

13 main striking region

14 character

16 grip

17 shaft

18 throat

20 retainer

21 inner radius

22 fastening portion

23 retainer

24 retainer portion

25 retainer inner surface

26 longitudinal structure

27 transverse structure

28 end of the retainer

29 rounded corners

30 holding device

32 lower holding tool

34 upper holding tool

35 threaded borehole

36 screw connection

38 material recesses

40 double-walled transverse web

42 wall portions

44 insertion device

46 string deflection surface of the retainer

47 line of symmetry/plane of symmetry

50 lower mold

52 upper mold

54 compressed air inlets

S gap

L1-L5 five different predetermined lengths of the retainers 20, 23 according to the invention 

1. A ball-striking device (1), in particular a tennis, squash, or badminton racket, having a head frame (2), which comprises a striking surface, is of a hollow design, and is produced from plastic, in particular from a fiber-reinforced plastic, and a shaft formed thereon with grip, wherein the striking surface (12) is defined by at least one string (8), which is tensioned in a crisscross manner and which forms string portions fastened substantially in parallel to one another on the head frame, wherein the anchoring of the string portions on the head frame (2) is performed via retainers (20) which are fastened on the inner side of the head frame so that they each extend substantially perpendicularly in relation to the striking surface, whereby the ends (10) of the string portions clamped in the retainers (20; 23) can be laterally deflected upon impact of a ball, characterized in that the retainers (20; 23) are open toward one of the two sides of the striking surface (12) and/or are freely accessible from one of the two sides of the striking surface (12) for clamping the string which defines the striking surface.
 2. The ball-striking device according to claim 1, characterized in that, for anchoring the string portions on the head frame, a set of retainers (20; 23) is provided, which comprises a first number of retainers having a first predetermined length (L1) in the circumferential direction of the head frame, at least one second number of retainers having a second predetermined length (L2) in the circumferential direction of the head frame, optionally at least one third, fourth, and fifth number of retainers having a third, fourth, and fifth predetermined length (L3, L4, L5) in the circumferential direction of the head frame.
 3. The ball-striking device according to claim 1, characterized in that the retainers (20, 23), in the state fastened on the head frame (2), each comprise a retainer portion (24) protruding therefrom and a fastening portion (22) anchored inside the head frame (2).
 4. The ball-striking device according to claim 3, characterized in that the fastening portion (22) of each retainer (20) has longitudinal (26) and transverse structures (27) for the formfitted and friction-locked anchoring inside the head frame (2).
 5. The ball-striking device, in particular according to claim 1, wherein the retainer portion (24) is designed as either open toward one side and/or freely accessible toward one side, in particular as hooked, preferably oval-hooked, or closed toward both sides, in particular ring-shaped, characterized in that the fastening portion (22) of each retainer (20; 23) is embedded between two frame halves (4, 6), which define the head frame (2).
 6. The ball-striking device according to claim 5, characterized in that the head frame (2) is formed by two frame halves, each made of a tubular prepreg (4, 6), which define a double-walled circumferential transverse web (40) extending approximately in parallel to the striking surface (12) approximately at the height of the striking surface (12), wherein the fastening portions (22) of the retainers (20; 23) are each embedded between the wall portions (42) of the two tubular prepregs (4, 6) defining the double-walled transverse webs (40) and are therefore fixedly anchored.
 7. The ball-striking device according to claim 1, characterized in that the inner radius (21) of the retainers (20; 23) is in a range from 0.5 to 1.9 mm.
 8. The ball-striking device according to claim 1, characterized in that the length of each of the retainers (20; 23) in the circumferential direction of the head frame is in the range from 5-30 mm, in particular the first predetermined length (L1) of the first number of retainers is in a range from 9-11 mm and/or the first number of retainers in the first predetermined length (L1) is 12 to 20, in particular 16, and/or the second predetermined length (L2) of the second number of retainers is in a range from 10-11 mm and/or the second number of retainers of the second predetermined length (L2) is 6 to 14, in particular 10, and/or the third predetermined length (L3) of the third number of retainers is in a range from 11-13 mm and/or the third number of retainers of the third predetermined length (L3) is 2 to 10, in particular 6, and/or the fourth predetermined length (L4) of the fourth number of retainers is in a range from 16-18 mm and/or the fourth number of retainers of the fourth predetermined length (L4) is 2 to 8, in particular 4, and/or the fifth predetermined length (L5) of the fifth number of retainers is in a range from 20-22 mm and/or the fourth number of retainers of the fourth predetermined length (L5) is 1 to 4, in particular
 2. 9. The ball-striking device according to claim 1, characterized in that the retainers (20; 23) of predetermined length are each identified with a character provided for the purpose of typing, in particular visually and/or haptically recognizable characters or also characters readable in any other readable or automatically analyzable form, which indicate the type of the retainer of predetermined length (L1; L2; L3; L4; L5).
 10. The ball-striking device according to claim 1, characterized in that a lateral gap (S) is defined between the free end of a retainer (20; 23) and the portion of the head frame (2) facing toward it, wherein the width of this gap is in the range from 1.0 to 2.0 mm, in particular in a range from 1.5 to 1.7 mm.
 11. The ball-striking device according to claim 1, characterized in that the frontal ends (29) of the retainers (20; 23), via each of which the string (8) defining the striking surface is deflected, are rounded.
 12. A method for producing a ball-striking device according to claim 1, wherein the retainers (20) are positioned in relation to a mold, within which a head frame (2) of a ball-striking device is produced, such that the fastening portions (14) of the retainers (20; 23) each protrude therein during the production of the head frame and are enclosed by the material thereof.
 13. The method for producing a ball-striking device according to claim 12, characterized by the following method steps: positioning a first prepreg tube (4) in a first, for example, lower head frame mold (50); positioning a second prepreg tube (6) in a second, for example, upper head frame mold (52); positioning a holding device (30) for the retainers (20; 23) held in the correct position therein between upper and lower head frame molds such that the fastening portions of the retainers (20; 23) protrude into a region between the first and second prepreg tube (4; 6); forming and curing the prepreg tubes (4; 6) in the closed head frame mold while embedding the retainer fastening portions (22); and cooling and demolding the finished produced head frame having retainers (20; 23) fixedly anchored on the frame inner side.
 14. The method for producing a ball-striking device according to claim 12, in which the frame, which consists of head frame (2) having retainers (20; 23), and also shaft (17) with grip (16) and optionally throat (18), is produced in one method step. 